1. Field of the Invention
The present invention: relates to an optical pickup device or use with an optical disk apparatus for recording and/or reproducing an optical disk which is a disk-like optical recording medium such as an optical disk and a magneto-optical disk.
2. Description of the Related Art
Optical pickup devices are generally for use with an optical disk apparatus. An optical disk apparatus, such as a CD player and a DVD player for reproducing an optical disk, includes an optical pickup device alone, and a magneto-optical disk apparatus for recording and/or reproducing a magneto-optical disk includes an optical pickup device combined with a magnetic head device serving as an overwrite head.
While this optical pickup device is able to read out a signal from an optical disk by irradiating laser beams on the optical disk, if the optical disk is encountered with a trouble such as a skew, then a laser beam irradiated from an objective lens is focused on a signal surface with an inclination. As a result, a focus of a laser beam is spread as an elliptical focus and reading of a signal becomes indefinite due to a crosstalk so that a picture quality is deteriorated when a video signal is read out from the signal surface.
For this reason, since laser beams should constantly be irradiated on the optical disk perpendicularly in order to accurately read out a signal from the optical disk, the optical pickup device detects a disk skew so as to constantly read a recorded signal with the best optical aberration state relative to the skew of the optical disk and reads (reproduces) a recorded signal by mechanically inclining the optical pickup device itself, i.e., adjusts a skew based on a detected signal.
As an optical disk apparatus in which the disk skew is detected and the optical disk is reproduced while the optical pickup device itself is being inclined mechanically, there is known an optical disk apparatus in which a mechanical chassis includes a pickup chassis having an optical pickup device which is driven with an inclination independently of a disk drive chassis including a spindle motor and a turntable, a sensor for detecting an inclination of a disk is disposed on this pickup chassis, this sensor detects an inclination of a disk surface relative to the optical axis of the optical pickup device and skew servo for adjusting an angle of the optical axis of the optical pickup device is effected by driving the pickup chassis with an inclination in accordance with the detected inclination.
In recent years, there has been sued an optical disk apparatus including an optical pickup device which introduces skew servo to calculate an optical jitter value by directly monitoring a jitter value of an RF signal of an optical pickup device without the sensor for detecting the inclination of the optical disk.
As the optical disk apparatus including the above optical pickup device, there is proposed an optical disk apparatus as shown in FIGS. 15 to 18.
A base chassis 2 of an optical disk apparatus 1 shown in FIGS. 15 to 18 is comprised of a spindle chassis 4 including a rotary drive mechanism 3 for rotating an optical disk D and a pickup chassis 6 including an optical pickup device 5 for reading out an information recording signal from the optical disk D rotated by the rotary drive mechanism 3 in such a manner that the optical pickup device can be moved.
The spindle chassis 4 is shaped as a substantially rectangular frame-like chassis. A front side portion 4a which is one end side of the longitudinal direction is substantially twice as high as other three side portions. Its top surface is inwardly extended and its central portion is protruded in the upper direction, thereby providing a motor attachment base 7. A spindle motor 8 is attached to the lower surface side of this motor attachment base 7. A rotary shaft 8a of this spindle motor is protruded to the upper surface side of the motor attachment base 7, and a turntable 9 is fitted into and fixed to the protruded end of the rotary shaft at a fitting portion 9a of the central portion. The spindle motor 8 and the turntable 9 constitute the rotary drive mechanism 3.
On the other hand, the pickup chassis 6 is substantially the same in shape as the three-side portion without the front side portion 4a of the spindle chassis 4, i.e., substantially U-letter shape of substantially the same size when viewed from a plan, and a coupling member 6a is extended between the front ends of the pickup chassis. This pickup chassis 6 is disposed on the spindle chassis 4 behind the front side portion 4a. In the inside of one side portion 6b of this pickup chassis 6, there is extended a feed screw shaft 10 of the optical pickup device 5 in the front and back direction so that the feed screw shaft may be pivotally supported at the front and rear ends. The feed screw shaft is coupled at its front end to a feed motor 11 attached to the front end face of the one side portion 6b. 
In the inside of another side portion 6c of the pickup chassis 6, there is extended a guide shaft 12 in parallel to the feed screw shaft 10. A cam member 13 is protruded from the upper front end of another side portion 6c. Shaft portions 14a, 14b are protruded from the lower sides of substantially the central portions of the outside of the two side portions 6b, 6c of this pickup chassis 6 and pivoted at bearing portions 15a, 15b provided at substantially the central portions of the two side portions 4b, 4c of the spindle chassis 4. While the shaft portions 14a, 14b of the pickup chassis 6 are being pivoted at the bearing portions 15a, 15b of the spindle chassis 4, a predetermined space is generated between the lower surface side of the pickup chassis and the upper surface side of the three-side portion of the spindle chassis 4.
The pickup chassis 6 pivotally disposed on the spindle chassis 4 as described above includes the optical pickup device 5 in such a manner that the optical pickup device can be moved close to or moved away from the disk rotary drive mechanism 3 attached to the front side portion 4a of the spindle chassis 4. Specifically, this optical pickup device 5 includes a slide member 17 with a biaxial actuator 16 for driving an objective lens 5a mounted thereon and which incorporates therein optical assemblies (not shown). This slide member 17 has a bearing aperture 17a defined at its one side. The feed screw shaft 10 at the one side portion 6b side of the pickup chassis 6 is inserted into this bearing aperture 17a so as to become freely slidable. A slide rack 18 attached to the lower surface of the slide member 17 is meshed with this feed screw shaft 10. A bearing portion of substantially U-letter shape is provided on the other side of the slide member 17 and tightly inserted into the guide shaft 12 on another side portion 6c of the pickup chassis 6 so as to become freely slidable. In this manner, the slide member 17 is supported by the feed screw shaft 10 and the guide shaft 12 and transported by a transport drive mechanism comprised of the feed screw shaft 10, the feed motor 11 and the slide rack 18, whereby the optical pickup device 5 is moved close to or moved away from the disk rotary drive mechanism 3.
Then, the pickup chassis 6 including this optical pickup device 5 is constantly displaced toward the other side portion 4c side with elasticity relative to the spindle chassis 4 and is tilted by a tilt drive mechanism 19. This tilt drive mechanism 19 is attached to the front side portion 4a of the spindle chassis 4 and is comprised of a tilt motor 20 attached to the lower surface side of the front side portion 4a, a tilt gear 21 fitted into and fixed to a rotary shaft of the tilt motor 20 protruded to the upper surface side and a tilt cam 22 pivotally supported to the upper surface side so as to be meshed with the teeth portion of the tilt gear 21 and which has a cam surface 22a formed on its upper end face.
A cam member 13 on the other side portion 6c of the pickup chassis 6 is opposed to the cam surface 22a of the tilt cam 22 of this tilt drive mechanism 19. A free end side of a leaf spring 24 fastened to and fixed to the upper surface of the front side portion 4a of the spindle chassis 4 by a fixing screw 23 is urged against the cam member 13 at its base end portion, whereby the cam member 13 is constantly urged against the cam surface of the tilt cam 22 under spring force of the leaf spring 24. In FIG. 15, reference numeral 25 denotes an actuator cover which covers the biaxial actuator 16 of the optical pickup device 5. This actuator cover has an opening 25a defined thereon to expose the objective lens 5a. 
In the disk drive apparatus 1 having the above arrangement, the optical disk D is held on and chucked to the turntable 9 of the disk rotary drive mechanism 3 and the turntable 9 is rotated by the spindle motor 8, whereby the optical disk D is rotated at a predetermined velocity.
At substantially the same time this optical disk D is rotated, the feed motor 11 of the feed mechanism of the optical pickup device 5 is driven and thereby the feed screw shaft 10 is rotated. Consequently, the slide member 17 is slid along the feed screw shaft 10 and the guide shaft 12 through the slide rack 18 meshed with the feed screw shaft 10, whereby the optical pickup device 5 is moved, i.e., moved in the direction in which the optical pickup device approaches to the turntable 9. The inclination of the disk D on the turntable 9 is detected by the movement of this optical pickup device 5.
The manner in which the inclination of the optical disk D is detected will be described below. When the optical pickup device 5 is moved in the radius direction from the outer peripheral side to the inner peripheral side of the optical disk D, time periods required until laser beams are returned after the laser beams have been irradiated on the information recording surface of the optical disk D from the objective lens 5a are detected continuously. Thus, it is possible to detect the inclination amount of the optical disk D by comparing the time periods thus detected.
Operations for correcting the thus detected inclination amount of the optical disk D will be described below. Assuming that the spindle chassis 4 and the pickup chassis 6 comprising the base chassis 2 are set to the relationship shown in FIG. 17, for example, i.e., the pickup chassis 6 is inclined toward the turntable 9 side relative to the spindle chassis 4, then when the inclination of the optical disk D is detected in this state, the tilt motor 20 is driven and rotation force of the tilt motor is transmitted to the tilt gear 21, whereby the tilt cam 22 meshed with this tilt gear 21 is rotated in response to a rotation amount of the tilt motor 20.
Since the cam member 13 of the pickup chassis 6 is urged against the cam surface 22a of the upper surface side of this tilt cam 22 under spring force of the leaf spring 24, the high portion surface of the cam surface 22a is brought in slidable contact with the cam member 13 by the rotation of the tilt cam 22 so that the pickup chassis 6 is pushed up through the cam member 13 and thereby rotated about the pivot portions based on the shaft portions 14a, 14b. Thus, when the highest position of the cam surface 22a of the tilt cam 22 is brought in a slidable contact with the cam member 13, the pickup chassis 6 is inclined rearwardly as shown in FIG. 18.
In this manner, the pickup chassis 67 is being inclined between the state shown in FIG. 17 and the state shown in FIG. 18, whereby the inclination of the optical pickup device 5 can be adjusted in response to the inclination of the optical disk 33 and the optical axis of the objective lens 5a can be opposed to the direction perpendicular to the information recording surface of the optical disk 33.
When the inclination of the optical pickup device 5 is adjusted in response to the inclination amount of the optical disk D by the adjustment of the tilt mechanism, the optical pickup device 5 reproduces an information signal from the information recording surface of the optical disk D. The manner in which the information recording signal is reproduced by this optical pickup device 5 will be described. Laser beams are irradiated on the information recording surface of the optical disk D from the objective lens 5a and reflected beams are received through the objective lens 5a, whereby the information signal is reproduced from that information recording surface.
As described above, in the disk drive apparatus 1, the optical pickup device 5 is incorporated in the pickup chassis 6 which is provided independently of the spindle chassis 4 including the disk rotary drive mechanism 3, this pickup chassis 6 is inclined by the tilt motor 20 and the tilt cam 22 of the spindle chassis 4, the posture of the optical pickup device 5 is corrected to the optical best point relative to the optical disk D rotated by the disk rotary drive mechanism 3, i.e., the jitter best point and the optical disk D is reproduced.
While the conventional optical pickup device of the optical disk apparatus such as a CD player and a DVD player is adapted to mechanically incline the optical pickup device itself in order that the information recording signal can constantly be read out under the optical best aberration state relative to the inclination of the rotating optical disk as described above, this optical pickup device having the arrangement in which the inclination of the optical disk is detected by a sensor or the like cannot be miniaturized without difficulty. Moreover, since this optical pickup device mechanically inclines itself, the arrangement becomes complicated and the number of assemblies increases, which as a result makes the optical pickup device expensive.
Also in the case of the optical pickup device in which the sensor for detecting the inclination of the optical disk or the like is deleted and which introduces the adaptive servo in which the optimum jitter value is calculated by directly monitoring the jitter value of the RF signal based on reflected beams from the optical disk, a mechanical mechanism such as the tilt mechanism for controlling the posture of the optical pickup device cannot be deleted, the arrangement thereof is complicated and the number of assemblies increases. This hinders the manufacturing cost from being decreased and also hinders the optical pickup device from being miniaturized.
In view of the aforesaid aspect, it is an object of the present invention to provide an optical pickup device for use in a disk drive apparatus in which an information recording signal can constantly be read out with the best optical aberration state relative to an inclination of an optical disk without using a mechanical tilt mechanism.
In order to attain the above objects, there is provided an optical pickup device including an objective lens drive mechanism comprising a movable-side member holding an objective lens for converging optical beams emitted from a light source on a signal recording surface of a disk-like optical recording medium, a supporting mechanism for supporting the movable-side member such that the movable-side member can be driven in the focusing direction and in the tracking direction relative to the disk-like optical recording medium and a drive force providing means for providing the movable-side member with driving force, wherein the movable-side member is driven with a predetermined inclination in the focusing direction in response to a focusing height changed due to a skew of the disk-like optical recording medium in such a manner that an optical axis direction of the objective lens becomes substantially perpendicular to the signal recording surface of the disk-like optical recording medium.
In the above arrangement, according to the present invention, the supporting mechanism is comprised of a fixed-side member and four supporting springs and spring constants of supporting springs located at the inner peripheral side of the disk-like optical recording medium are made larger than those of supporting springs located at the outer peripheral side so that the predetermined inclination is generated when the movable-side member is driven in the focusing direction.
In the above arrangement, the supporting springs make spring constants of supporting springs of the inner peripheral side become larger than those of supporting springs of the outer peripheral side by changing diameters of wires.
In the above arrangement, according to the present invention, the driving mechanism includes a magnetic circuit and a center of the magnetic circuit is shifted in the outer peripheral direction relative to the disk-like optical recording medium such that the predetermined inclination is generated when the movable-side member is driven in the focusing direction.
In the above arrangement, the magnetic circuit displaces its center in the outer peripheral side by increasing a space between a yoke fitted into a hollow portion of a focusing coil wound around the movable-side member in the inner peripheral side relative to the disk-like optical recording medium and by decreasing the space in the outer peripheral side relative to the disk-like optical recording medium.
In the above arrangement, according to the present invention, the driving mechanism includes a magnetic circuit, the magnetic circuit has a center shifted in the outer peripheral direction relative to the disk-like optical recording medium, the supporting mechanism is comprised of a fixed-side member and four supporting springs and the predetermined inclination is generated by suppressing elastic force of supporting springs located at the inner peripheral side relative to the disk-like optical recording medium when the movable member is driven in the focusing direction.
In the above arrangement, the magnetic circuit shifts its center in the outer peripheral side by increasing a space between a yoke fitted into a hollow portion of a focusing coil wound around the movable-side member and the focusing coil in the inner peripheral side relative to the disk-like optical recording medium and by decreasing the space in the outer peripheral side relative to the disk-like optical recording medium, the supporting mechanism includes four supporting springs to which damping materials are bonded and elastic force of supporting springs located at the inner peripheral side is suppressed by increasing an amount of damping materials of the supporting springs located at the inner peripheral side relative to the disk-like optical recording medium than that of damping materials of the supporting springs located at the outer peripheral side.
In the optical pickup device having the above arrangement according to the present invention, since the movable-side member holding the objective lens of the objective lens drive mechanism is driven with the predetermined inclination in the focusing direction in response to the amount in which the height of focus is changed due to the skew of the disk-like optical recording medium so that the Q axis of the objective lens becomes substantially perpendicular to the signal recording surface of the disk-like optical recording medium, the optical pickup device is able to reproduce the recorded signal reliability.
Then, according to the present invention, the tilt mechanism for detecting the skew of the disk-like optical recording medium and adjusting the tilt can be deleted from the optical pickup device, and hence the arrangement of the disk drive apparatus can be simplified.